Neonatal immune challenge poses a sex-specific risk for epigenetic microglial reprogramming and behavioral impairment

While the precise processes underlying a sex bias in the development of central nervous system (CNS) disorders are unknown, there is growing evidence that an early life immune activation can contribute to the disease pathogenesis. When we mimicked an early systemic viral infection or applied murine cytomegalovirus (MCMV) systemically in neonatal female and male mice, only male adolescent mice presented behavioral deficits, including reduced social behavior and cognition. This was paralleled by an increased amount of infiltrating T cells in the brain parenchyma, enhanced interferon-γ (IFNγ) signaling, and epigenetic reprogramming of microglial cells. These microglial cells showed increased phagocytic activity, which resulted in abnormal loss of excitatory synapses within the hippocampal brain region. None of these alterations were seen in female adolescent mice. Our findings underscore the early postnatal period’s susceptibility to cause sex-dependent long-term CNS deficiencies following infections.


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Bulk RNA sequencing datasets were deposited into the Gene Expression Omnibus database under accession number GSE198473 and are available at the following URL: https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE198473.
There were no human research participants involved in this study.
There were no human research participants involved in this study.
There were no human research participants involved in this study.
There were no human research participants involved in this study.
Sample size is similar to sample sizes routinely used in the field for histological and behavioral comparisons (see Kaphzan et al. Cell Rep (2013), Quintana et al. Nat Neurosci (2012), Zhang et al. Neuropsychopharmacology (2002 No data or mice were excluded.
If not indicated otherwise, all experiments were performed once.
In all behavioral assays, subjects were randomly assigned to a group and the experiments were blind with respect to group assignments. Animals used for each experiment are littermates randomly assigned to the experimental groups.

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Our study focuses on sex-specific effects upon neonatal immune stimulation. We have therefore analysed both male and female mice. Data is shown disaggregated for sex.
The study did not involve samples collected from the field.
Animal experiments were performed with the approval of the Regional Council of Freiburg, Germany, and the Research Ethics Committee at Leiden University, Leiden, Belgium. Experiments were carried out in accordance with the Fundamental Guidelines for Proper Conduct of Animal Experiment and Related Activities in Academic Research Institutions at the University of Freiburg, Germany.
Spleens from naive and MCMV-infected mice were mechanically dissociated in Dissection Media and passed through a 100 um cell strainer. Red blood cells were lysed using RBC Cell Lysis buffer. Splenocates were counted on a hemocytometer and seeded in 5 ml FACS tubes at a density of 1,000,000 cells/mL and stimulated with PMA 50 ng/mL) and ionomycin (1 uM) for 3 hours. Cells were then collected by centrifugation and stained for FACS analysis.